Featured Research

from universities, journals, and other organizations

First Image Of Black Hole's "Shadow" May Be Possible Soon

Date:
December 16, 1999
Source:
Johns Hopkins University
Summary:
A "picture" of the massive black hole thought to be lurking at the heart of our home galaxy may be within astronomers' reach in the next few years.

Related Articles


Heino Falcke, MPIfR (Europe, 6 hours ahead of U.S. EST)
work: 011 49 228 525 217 (until 12 noon EST)
home: 011 49 2234 15635(after 12 noon EST)

A "picture" of the massive black hole thought to be lurking at the heart of our home galaxy may be within astronomers' reach in the next few years, according to a report in the Jan. 1, 2000, edition of "Astrophysical Journal Letters."

The paper (available now in an electronic preprint) predicts that upcoming improvements in scientific techniques could permit astronomers to see how a narrow escape from the black hole's clutches twists, dims, and amplifies radio waves.

Such observations should reveal a circular shadow at the heart of the galaxy – the first image of a black hole's event horizon – according to a computer model created by theorists at The Johns Hopkins University, the Max-Planck-Institut fuer Radioastronomie in Germany, and the University of Arizona.

The event horizon is thought to be the defining feature of a black hole, a point-of-no-return surrounding the hole inside which even light cannot escape the black hole's gravity. Imaging this would be a final step in the black hole's journey from curious theoretical oddity to cosmic reality.

"Regardless of the structure of the region around the black hole that we tried in our computer models, we saw a shadow in the simulated images," says Eric Agol, a postdoctoral researcher at Hopkins and an author of the paper. "This paper is our way of trying to interest astronomers in working together to perform the actual observations, which could produce very exciting results."

Agol cautions that the same plasma that emits radio waves near the black hole might also block the radio waves needed to "see" the hole – an effect not included in the models. This could be circumvented by observing at even shorter wavelengths, where the plasma becomes transparent and the black hole shadow will appear. "This would make it harder to see it from the ground, but it should always be possible to see it from space," Agol says, noting that some shorter wavelengths are blocked by Earth's atmosphere.

So far, scientists have only been able to indirectly detect black holes by observing their effects on the orbits of nearby stars or by detecting the powerful radiation given off by gas and other material being pulled into the black hole.

Astronomers have seen these effects in the centers of other galaxies. The Milky Way's center can't be seen in visible light because there's too much interstellar gunk in the 25,000 light years between Earth and the galactic center. But longer-wavelength radiation like infrared radiation and radio waves can make it through relatively unscathed.

"At Sagittarius A star [Sagittarius A*], a point at or near our galaxy's center, astronomers have found a compact source of very strong radio emission, perhaps created by highly ionized gas surrounding a black hole," says Heino Falcke, research scientist at Max-Planck-Institut and lead author on the paper. "Infrared observations of the same region show rapidly moving stars pulled around by a very concentrated mass at the same position as the radio source Sagittarius A*. This is probably the best evidence that we have for a black hole so far, but not decisive proof."

To zoom in further on the radio wave emission in this area, scientists have used a technique known as Very Long Baseline Interferometry (VLBI). By coordinating and comparing the results they receive from different radio telescopes, they can produce an image with greater detail and resolution than the individual radio telescopes could on their own.

"The resolving power is equivalent to what you'd get if you had a radio telescope as large as the telescopes you're combining and the area between them," says Falcke. "This can be as large as the size of the Earth."

Astronomers at the Max-Planck-Institut and elsewhere have been working to use VLBI to observe shorter wavelengths of radio emission, a technique known as millimeter-VLBI. By pushing VLBI to the shortest wavelengths and highest spatial resolutions available in astronomy, they have already come very close to the resolution that should be needed to see the shadow.

"I think we didn't realize before how close the technique is to detecting this shadow," Falcke says. "With the currently available resolution, we could ‘see' from Berlin, Germany, a radio source in Los Angeles the size of a mustard seed. Now we have to improve things just to the point where we can image a dent on the seed."

"The improvements necessary to test this prediction are within reach and should become feasible over the next few years," says Anton Zensus, director at the Max-Planck-Institut and leader of the VLBI group.

For the paper, the authors took what astronomers currently know about the mass of Sagittarius A* and plugged it and other potential features of the black hole, such as its rotation, into a "relativistic ray-tracing" program Agol had developed. The program traces the path of electromagnetic radiation through space warped by the tremendous gravity of a black hole.

"You can think of it as taking each photon of radiation emitted somewhere near the black hole and following its path to the observer," explains Fulvio Melia, astrophysicist from the University of Arizona and co-author on the paper. "The program calculates the effects of the black hole on the radiation's path and wavelength, effects that are very precisely predicted by Einstein's Theory of General Relativity."

"A similar, simplified calculation was made by physicist James Bardeen in the 1970s," says Agol. "At that time, we didn't have as much information on the galactic center, so his work was considered by many to be a purely theoretical exercise."

Given the resolution achievable at short radio wavelengths, the new calculations showed a distinctive pattern in radiation from Sagittarius A*: a circular shadow.

"With the major observatories working together, and a further improvement of millimeter-VLBI, we should soon be able to actually image the shadow of a black hole. This would be the final test of whether black holes and event horizons exist," says Falcke.

Since demand is high for time at radioastronomy observatories, he acknowledges, that would take no small amount of money, effort and sacrifice. But because of the potentially tremendous step forward this effort might produce, he and the other authors strongly feel the challenge is worthwhile.

This research was supported by Melia's Sir Thomas Lyle Fellowship and grants from NASA, DFG (Deutsche Forschungsgemeinschaft), and the National Science Foundation.

###

For more information, see "The Black Hole in the Galactic Center," a slide show by Heino Falcke. Included in the show are an MPEG movie simulating a zooming view into the Galactic Center and the black hole (slide 14), and color images (GIFs) of the shadow seen in the author's calculations (slides 11 and 12).


Story Source:

The above story is based on materials provided by Johns Hopkins University. Note: Materials may be edited for content and length.


Cite This Page:

Johns Hopkins University. "First Image Of Black Hole's "Shadow" May Be Possible Soon." ScienceDaily. ScienceDaily, 16 December 1999. <www.sciencedaily.com/releases/1999/12/991215103043.htm>.
Johns Hopkins University. (1999, December 16). First Image Of Black Hole's "Shadow" May Be Possible Soon. ScienceDaily. Retrieved January 30, 2015 from www.sciencedaily.com/releases/1999/12/991215103043.htm
Johns Hopkins University. "First Image Of Black Hole's "Shadow" May Be Possible Soon." ScienceDaily. www.sciencedaily.com/releases/1999/12/991215103043.htm (accessed January 30, 2015).

Share This


More From ScienceDaily



More Space & Time News

Friday, January 30, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

NASA Holds Memorial to Remember Astronauts

NASA Holds Memorial to Remember Astronauts

AP (Jan. 29, 2015) NASA is remembering 17 astronauts who were killed in the line of duty and dozens more who have died since the agency&apos;s beginning. A remembrance ceremony was held Thursday at NASA&apos;s Marshall Space Flight Center in Alabama. (Jan. 29) Video provided by AP
Powered by NewsLook.com
Asteroid's Moon Spotted During Earth Flyby

Asteroid's Moon Spotted During Earth Flyby

Rumble (Jan. 27, 2015) Scientists working with NASA&apos;s Deep Space Network antenna at Goldstone, California discovered an unexpected moon while observing asteroid 2004 BL86 during its recent flyby past Earth. Credit to &apos;NASA JPL&apos;. Video provided by Rumble
Powered by NewsLook.com
Water Fleas Prepare for Space Voyage

Water Fleas Prepare for Space Voyage

Reuters - Innovations Video Online (Jan. 26, 2015) Scientists are preparing a group of water fleas for a unique voyage into space. The aquatic crustaceans, known as Daphnia, can be used as a miniature model for biomedical research, and their reproductive and swimming behaviour will be tested for signs of stress while on board the International Space Station. Jim Drury went to meet the team. Video provided by Reuters
Powered by NewsLook.com
Mars Rover Opportunity Celebrates 11-Year Anniversary

Mars Rover Opportunity Celebrates 11-Year Anniversary

Rumble (Jan. 26, 2015) Eleven years ago NASA&apos;s Opportunity rover touched down on Mars for what was only supposed to be a 90-day mission. Since then it has traveled 25.9 miles (41.7 kilometers), further than any other off-Earth surface vehicle has ever driven. Credit to &apos;NASA&apos;. Video provided by Rumble
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins